This invention relates to a controller for a vehicle suspension and more particularly to an active suspension control system for a vehicle. This active suspension control system gives a driver good ride and handling.
An active syspension control system is described in, for example, Automotive Engineer, February/March 1984, pp. 56-57. This system is an active suspension system installed in a racing car and developed by Lotus (Britain). In this system, springs, dampers and anti-roll bars, all used in the conventional suspension, are not employed but instead pressure oil actuators fill the role of the springs and dampers to support the vehicle boby. Oil is permitted to enter or leave the pressure oil actuator by controlling a servo valve and an oil pump driver by part of the output of the engine. This active suspension system has a total weight of 40 Kg and requires 3.7 kW peak energy. In operation, a number of parameters, including longitudinal and lateral accelerations at the center of gravity of the body, relative displacement between the body and the wheel, longitudinal acceleration of the wheel and longitudinal load from the body, are detected and subjected to a sophisticated arithmetic processing at an electronic control unit to produce a command signal supplied to the servo valve which, in turn, controls the charging and discharging of oil to and from chambers above and below the actuator piston to optimize the body attitude, feeling of ride and handling (controllability). This system is on the one hand advantageous in improving the feeling of the ride, stability of the body attitude and in increasing the speed of the vehicle through corners. For example, the speed through corners can be as much as 10% with this system. However, the Lotus system is very complicated and expensive and consumes a large amount of power for driving the oil pump (a concomitant increase in energy consumption in the engine), thus facing difficulties in its application to automobiles produced on a mass production basis. The large energy consumption degrades fuel economy in the automobile.